News from the Bench

Discover what’s going on at CST, receive our latest application notes and tips, read our science features, and learn about our products.


Antibody Guarantee

CST Antibody Performance Guarantee


To get local purchase information on this product, click here


Find answers on our FAQs page.


Visit PhosphoSitePlus®

PTM information and tools available.


Top: SK-N-MC cells were pretreated with varying amounts of PD980559 for 1 hour, then treated with FGF for 30 minutes. Cell extracts were blotted with Phospho-p44/p42 MAP Kinase (Thr202/Tyr204) Antibody #9101. Middle: COS cells were transfected with pCMV-MKK3 for 22 hours, pretreated with varying amounts of PD98059 for 1 hour, then treated with anisomycin for 30 minutes. Cell extracts were blotted with Phospho-MKK3/MKK6 (Ser189/207) Antibody #9231. Lower: 293 cells were pretreated with varying amounts of PD98059 for 1 hour, then treated with sodium chloride for 30 minutes. Cell extracts were blotted with Phospho-SEK1/MKK4 (Thr261) Antibody #9151.

Learn more about how we get our images

Product Usage Information

Supplied as a lyophilized yellow powder. For 20 mM stock, reconstitute 1.5 mg in 280 µl DMSO (5 mg in 933.3 μl). For 50 mM stock, reconstitute 1.5 mg in 112 µl DMSO (5 mg in 373.3 μl). Store in aliquots at -20ºC. See enclosed MSDS for further information. This product is for in vitro research use only and is not intended for use in humans or animals.

PD98059 is soluble in DMSO at 10-100 mM. For use with in vitro or cell-based assays, it may be diluted into aqueous buffers to yield desired concentrations (<100 µM) with final DMSO concentrations of ~0.1%. IC50 values for inhibitory activity against MEK1 are around 5-10 µM. For experiments with cultured cells, CST recommends pretreating with this inhibitor for one hour prior to stimulation.

Storage: Store lyophilized or in solution at -20ºC, desiccated. In lyophilized form, the chemical is stable for 24 months. Once in solution, use within 3 months to prevent loss of potency. Aliquot to avoid multiple freeze/thaw cycles.

Product Description

Molecular Weight:

267.28 g/mol



Molecular Formula:


MEK1 and MEK2, also called MAPK or Erk kinases, are dual-specificity protein kinases that function in a mitogen activated protein kinase cascade controlling cell growth and differentiation (1-3). Activation of MEK1 and MEK2 occurs through phosphorylation of two serine residues at positions 217 and 221, located in the activation loop of subdomain VIII, by Raf-like molecules. MEK1/2 is activated by a wide variety of growth factors and cytokines and also by membrane depolarization and calcium influx (1-4). Constitutively active forms of MEK1/2 are sufficient for the transformation of NIH/3T3 cells or the differentiation of PC-12 cells (4). MEK activates p44 and p42 MAP kinase by phosphorylating both threonine and tyrosine residues at sites located within the activation loop of kinase subdomain VIII.

PD98059 has been shown to act in vivo as a highly selective inhibitor of MEK1 activation and the MAP kinase cascade (1-4). PD98059 binds to the inactive forms of MEK1 and prevents activation by upstream activators such as c-Raf (3).

1.  Crews, C.M. et al. (1992) Science 258, 478-480.

2.  Alessi, D.R. et al. (1994) EMBO J. 13, 1610-1619.

3.  Rosen, L.B. et al. (1994) Neuron 12, 1207-1221.

4.  Cowley, S. et al. (1994) Cell 77, 841-852.

For Research Use Only. Not For Use In Diagnostic Procedures.
Cell Signaling Technology is a trademark of Cell Signaling Technology, Inc.